1. Technical Field
The present inventions relate to PCM to a set of digital PWM signals and, more particularly, relate to PCM to a set of digital PWM signals for multiple switch power stage control.
2. Description of the Related Art
Envelope Tracking is a method of powering the RF (radio frequency) power amplifier using a power signal which is a function of the RF signal envelope to improve power conversion efficiency of an RF envelope. As bandwidth of the RF signal increases for newer signals like 3G and 4G cellular standards, there is a move towards the use of digital circuitry to create the PWM (pulse width modulation) signals. The switching frequency of the PWM signal has to be significantly greater than the bandwidth of the RF signal envelope. As the bandwidth of the RF signal envelope goes into tens of MHz (megahertz) and higher the switching frequency of the PWM would get into the hundreds of MHz. The efficiency of a switching signal operating at such a high switching frequency is low due to the switching losses associated with the PWM power stage. As a result the efficiency of the envelope tracking RF power amplifier is reduced which is highly undesirable.